!! Update !!
Linux users, using Bottles to play the game !
Important, if you want to play on the Crossfire server.
*Download my *hta file and check the IP which I've manually added there - you'll need to add it in YOUR *hta file* ( PATH is : /.var/app/com.usebottles/data/bottles/bottles/*YOUR_CROSSFIRE_FOLDER_GAME_NAME*/drive_c/Freelancer Crossfire/EXE )
Locate your fldirectip.hta file and open it using Chrome based browser ( I've used Brave ) or vim/nano/gedit... whatever, to check if the IP section is empty ( as it should be ).
Add the IP provided in my config file ( using a text editor ), exactly how I added it ( do NOT attempt any other wizard moves or you'll end up reinstalling the whole thing. We're EMULATING, remember ? ).
Side note : While I was playing SP, I choose Win10. Game runs without problems - completed the campaign with no issues ( excluding the transport to Sol xD ).
Now I have changed the bottle to run like Win7 ( no speciffic reason for that, just a theory ). So if, for some reason your game faces any sort of issues after following these steps, try to run the application under Win7 - should work.
RTFM -> read & double read please
Open up Bottles, select the Bottle you are using to run the Crossfire executable ( No, do NOT run it !! )
Scroll down to the "DEPENDENCIES" menu ( for THAT SPECIFFIC BOTTLE ) and select it
Once inside the Dependencies menu, scroll down unitl you see : DirectPlay -> install it
Wait for the process to complete. Close the Bottles entirely ( "killall" if needed )
Open up Bottles again, run the Crossfire Freelancer exe, select Multiplayer, LAN ( ! Not Internet ! ) - voila !
I'd like to thank SWAT_OP-R8R for the help provided.
In order to check if the application ( Crossfire Freelancer exe ) is establishing connection via UDP port 2302, I had to find a way to check it, since Im sandboxing everything ( means, isolating everything via Flatseal ). His answer gave me the exact information I needed
*Check those ports, but no, you're not doing it the "normie way" via terminal ( isolated apps act differently ), use another emulation to "trick" the isolation -> DirectPlay ( flatsealed and configured for my use case. Might not be the same for you, don't worry )
Profit - server should be rite dere ! n'joy, you're welcome